Titanium containing precipitates



Patented Aug. 31, 1937 TITANIUM CONTAINING PRECIPITATES Paul Weise, Leverkusen-I. G. Werk, Germany, as-

. sig'nor, by mesne assignments, to National Lead Company, New York, N. Y., a corporation of New Jersey No Drawing. Application January 27, 1934, Serial No. 708,702. In GermanyFebruary 23, 1933 17 Claims. (01134-58) The present invention relates to titanium containing precipitates and to a process of preparing the same. l

In accordance with the present invention 'titanium containing precipitates are prepared by precipitating titanium hydroxide from titanium salt solutions in the presence of finely dispersed salts of titanium which are diflicultly soluble in dilute mineral acids. Such salts, which are difiicultly soluble in mineral acids are, for example, titanium phosphates, titanium potassium sulfates, titanium potassium fluorides, titanium silicates'and titanium zirconium compounds. These salts are prepared in the known manner, for instance, by double decomposition of a soluble titanium salt with asoluble other saltor acid'yielding a titanium salt which is difiicultly soluble in dilute acids (compare, for instance, Mellor, A Comprehensive Treatise on Inorganic and Theoretical Chemistry, Vol. VII (1927) page,22, second paragraph, lines 11-13, page 95,- lines 16-19, paragraph 3, lines 5-8) These salts are used in a dispersed state which is obtainable, for instance, by ionic reactions as by adding to a titanium salt solution a small amount of a solution of a soluble salt or the corresponding acid which forms a difiicultly soluble salt with the titanium. The quantity of the added salt oracid must be so chosen that the precipitated diflicultly soluble salt is still colloidally solublein the excess of the titanium salt solution used. The precipitate obtained thereby is stirred until it is transformed into a sol of the diflicultly soluble salt. When heating the sol obtained the difllcultly soluble salt coagulates, whereby the degree of dispersion of the salt can be regulated in the known manner by the degree of temperature, the duration of the heating process and the concentration and acid content of the solution. Although, to some extent other known processes of preparing finely dispersed precipitates can be applied the best results are obtained from the use of a finely dispersed titanic salt precipitated from aqueous solution converted to a sol and coagulated to a fine dispersion. The finely dispersed salt is added to the titanium solution to be precipitated.- Itis evident that it-is not necessary to coagulate the salt before adding it to the solution to be precipitated. The process can also be carried out by adding the sol to the solution to be precipitated and coagulating the diflicultly soluble salt in the solution, for instance, by heating. It is not even necessary to prepare the sol outside the solution to be precipitated; the process can be effected by adding the soluble salt or acid, yielding with the titanium salt a difiicultly soluble salt, to the titanium salt solution to be precipitated, stirring the precipitate obtained until it is converted into a sol and precipitating the difficultly soluble salt together with the titanium hydroxide. The precipitation of the titanium hydroxide from the titanium salt solution containing the finely dispersed difiicultly solublesalt can be efiected in the known manner by hydrolysis, for instance, by heating,'by adding alkaline reacting compounds or also by diluting with water. The quantity of the added diiiicultly soluble titanium salt can be varied within wide limits; in general 2 to 6% are added calculated on the quantity of titanium dioxide tobe precipitated.

The process is adaptable for the preparation of pure titanium pigments from titanium salt solutions as, for instance, sulfuric acid or hydrochloric acid solutions, and also for the preparation of, composite titanium pigments, the precipitation being effected in the presence, for instance, 0 of BaSOi; CaSO4, SiOz or other fillers, By the use ofthese finelydispersed difiicultly soluble salts the precipitation of the titanium hydroxide is accelerated and the grain size becomes finer 25 and more even than without the use of the finely dispersed salts. V

A process is particularly important in which the precipitation of titanium hydroxide from titanium salt solutions takes place in the presence of a finely dispersed titanium-phosphate. The products obtained thereby, containing intimately incorporated a small amount of titanium phosphate yield after calcination titanium pigments of great fineness possessing high coloring power and hiding power inwhich the titanium dioxide possesses a crystalline structure which is partly that of rutile and which do not give ofl phosphoric acid when treated with weakly acid solutions. o

By calcining the products obtained in accordance with the process of the present invention pigments are obtained which display remarkably good pigment properties. Thus they possess a bright white color, .high coloring and hiding 5 power and excellent resistivity to weather. The invention is further illustrated by the following examples without being restricted thereto:

Example 1.80 cos. of H3PO4 containing 220. grams of P205 per liter (or the equivalent quan- 50 tity of a soluble phosphate) are added to 1 liter of a cold solution of titanium sulfate containing in 1 liter grams of T102, 50 grams of Fe, in the form of F6504 and 230 grams of H9804,"

while stirring- A voluminous precipitate sep- 56' 2 I -moon-2'99 arates which afterstirring for about 20 hours completely disappears. Thus it becomes possible to obtain a solution which. contains up to 40 grams or P205 in 1 liter. This solution is added 5 to a titanium sulfate solution in such a quan-. tity that the precipitate obtained after. the hydrolysis has been eflected contains 1% of P205. It is also possible to heat the sol oi the titanium phosphate alone and to add this sol.

before or during the precipitationoi the titanium hydroxide. The titanium phosphate can also be prepared in the solution which is to be hydrolized.

The precipitation 01' the titanium hydrate takes place according to known conditions. The

precipitate is washed and calcined. A pigment of which-30% of the titanium dioxide content has the crystalline structure of rutile possessing high coloring power and a bright white. color is 20 thus obtained.

" Example 2.55 grams of K2504 are added in a concentrated solution to 1 liter of a titanium sulphate solution containing in 1 liter 120 grams of T102, 40 grams of Fe in the form of FeSO4and280 grams of H2804. A precipitate of potassium titanium sulfate is formed which after 12 hours stirring completely disappears. The solution is then heated to boiling whereby first finely divided tita ium potassium sulfate is precipitated which has a nucleating efiect and whereupon all the titanium is precipitated in a finely divided form on further heating. It is possible to precipitate'the finely dispersed titanium potassium sulfate alone and then add it to a titanium sulfate solution. The precipitate is washed and calcined. A pigment of high coloring power is thus obtained.

The expression titanium salt solution as used in this description is meant to include solu- 40 tions in which substantially all the titanium present is in titanic condition, i. e. tetravalent titanium. It will be understood that in titanic 'salt solutions used for the precipitation oi titanium hydroxide to be employed in the manufacture of titanium pigments there is usually present a small amount of reduced or trivalent titanium. The expressions titanium salt solution as used in this description and titanic salt solution" as used in the claims appended hereto are meant to include such solutions which contain a relatively small amount of-trivalent titanium. l

I claim: l

1. The process of hydrolytically precipitating titanium hydroxide from a titanic salt solution,

which comprises converting into a sol an inorganic titanic salt resulting -from a reaction between a solution 01a soluble inorganic titanium salt and a solution of a compound which with tetravalent titanium yields an inorganic titanic salt diificultly' soluble in dilute mineral acids but colloidally soluble in excess of the said soluble inorganic titanic salt coagulating the said sol, adding the sol tothe said titanic salt solution and heating the mixture.

2. The process of hydrolytically precipitating titanium hydroidde from a titanic salt solutior. which comprises converting a titanium plies.- phate into a sol, coagulating the sol, addinr, the

7 sol to the said titanic salt solution and heating the mixture.

3. In a process for hydrolytically precipitating titanium hydroxide from a titanic salt 'solution,

the steps which consist in adding a sol of an inorganic titanic salt resulting from a reaction between a solution of a soluble inorganic titanium salt and a solution of a compound which with tetravalent titanium yields an inorganic titanic salt difllcultly soluble in dilute mineral acids but colloidally soluble in excessof the said 5 soluble inorganic titanic salt to a titanic salt solution and heating the mixture to produce coagulation of the said titanic salt in a finely dispersed condition within the said titanic salt solution. 10

4. The process for hydrolizing a titanic salt solution which comprisesheating the said solution in the presence of a finely dispersed inorganic titanic salt resulting from a reaction between a solution of 'a soluble inorganic titanium 15 salt and a solution of a compound which with tetravalent titanium yields an'inorganic titanic salt difficultly soluble in dilute mineral acids but colloidally soluble in excess of the said soluble inorganic titanic salt and which is capable of 20 acceleratingthe hydrolytic decomposition of the said titanic salt solution.

5. The process for hydrolizing a titanic salt solution which comprises heating the said solution in the presence of a finely dispersed titanium 2s phosphate which is capable of accelerating the hydrolytic decomposition of the said titanic sal solution.

6. Process of preparing aprecipitate containing titanium-oxygen compounds which com- 30 prises precipitating by thermal hydrolysis titanium hydroxide from a titanic saltsolution in the presence of a small amount of a finely dispersed inorganic titanic salt cbagulated from a action between a solution of a soluble inorganic titanic salt and a solution of a compound which with tetravalent titanium yields an inorganic titanic salt difllcultly soluble in mineral acids but 40 colloidally soluble in an excess of the solution of said soluble inorganic titanic salt.

"1. Process of preparing a precipitate containing titanium-oxygen compounds which comprises precipitating by thermal hydrolysis titanium hy- 4;,

droxide from a titanic salt solution in the presence of a small amount of a finely dispersed titanium phosphate coagulated from a sol oi titanium phosphate said titanium phosphate resulting from a reaction between a solution of a soluble 50 inorganic titanic salt and a solution containing phosphate ions.

8. Process of preparing a precipitate containing titanium-oxygen compounds which comprises precipitating by thermal hydrolysis titanium hy- 55 droxide from a titanic salt solution in the pres- .ence of a filler and a small amount of a finely dispersed inorganic titanic salt ,coagulated from a sol or an inorganic titanic salt, said finely dispersedsalt resulting from a reaction between a 60 solution of a soluble inorganic titanic salt and a solution of a compound which with tetravalent titanium'yields an inorganic titanic salt diflicultly soluble inorganic in mineral acids but colloidally soluble in an excess of the solution of said soluble 65 titanic salt.

9. lrocess of preparing a precipitate containing-titanium-oxygen compounds'which comprises precipitating by thermal hydrolysis, titanium hydroxide from a titanic salt solution in the presf0 ence of a small amount or a finely dispersed inorganic titanic salt coagulated from a sol 01 an inorganic titanic salt, said finely dispersed titanic salt resulting. mm a reaction between a solution of a soluble inorganic titanic salt and a solution 76 itating titanium hydroxide from a titanic salt solution in the presence of a small amount of a finely dispersed inorganic titanic salt, said finely dispersed inorganic titanic salt resulting from a reaction between a solution of a soluble inorganic titanic salt and a solution of a compound which with tetravalent titanium yields an inorganic titanic salt diflicultly soluble in mineral acids but colloidally soluble in an excess of the solution of said soluble inorganic titanic salt.

11. In the process of preparing a composition of matter comprising calcined titanium dioxide possessing a crystalline structure which is partly that of rutile and having intimately incorporated therewith a finely dispersed inorganic titanic salt, the step which consists in hydrolytically precipitating titanium hydroxide from a titanic salt solution in the presence of a small'amount of a finely dispersed titanium phosphate coagulated from a sol of titanium phosphate said titanium phosphate resulting from a reaction between a solution of a soluble inorganic titanic salt and a solution containing phosphate ions.

12. In the process of preparing a composition of matter comprising calcined titanium dioxide soluble inorganic titanic salt and a solution of a. compound which with tetravalent titanium yields an inorganic titanic salt difllcultly soluble in mineral acids but colloidally soluble in an excess of the solution oi said soluble inorganic titanic salt.

13. In the process of preparing a composition of matter comprising calcined titanium dioxide possessing a crystalline structure which is partly that of rutile and having intimately incorporated therewith a finely dispersed inorganic titanic salt, the step which consists in hydrolytically precipitating titanium hydroxide from a titanic salt solution in the presence of a small amount of a nucleating finely dispersed inorganic titanic salt,

said salt resulting from a reaction between a solution of a soluble inorganic titanic salt and a solution of a compound which with tetravalent titanium yields an inorganic titanic salt difficultly soluble in mineral acids but colloidally soluble in an excess of the solution of said soluble inorganic titanic salt.

14. Process of preparing a precipitate con taining titanium-oxygen compounds which comprises precipitating by thermal hydrolysis titanium hydroxide from a titanic salt solution in the presence of a small amount of a finely dispersed titanium-silicate coagulated from a sol of titanium silicate, said titanium silicate resulting from'a reaction between-a solution of a soluble inorganic titanic salt and a solution containing silicate ions.

15. Process of preparing a precipitate containing titanium-oxygen compounds which comprises precipitating by thermal hydrolysis titanium hydroxide from a titanic salt solution inthe presence of a small amount of a finely dispersed titanium potassium sulfate coagulated from a sol of a titanium potassium sulfate resulting from a reaction between a solution of a soluble inorganic titanic salt and a solution containing potassium sulfate.

16. A pigment composition comprising a coprecipitated calcined mixture of titanium dioxide possessing a crystalline structure which is partly a PAUL wmsn. 

